Metallic circuit for multiple switch-boards



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- J.A.SEELY. I METALLIC OIROUIT FOR MULTIPLE SWITCH BOARDS.

No. 357,539. Patented Feb. 8, 1887.,

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(No Model.) 2 Sheets-Sheet 2.

. JQAISEE LYQ METALLIC CIRCUIT FOR MULTIPLE SWITCH BOARDS. v No. 357,539. Patented-Feb. 8, 1887.

I llllllllll \IIIIIIIIIIIIIIIH Switch-Boards, (Case 4,) of which the followzen of the United States, residing at New York,

JOHN A. SEELY, on NEW YORK, N. Y.

PATENT Fries.

, ASSIGNOR TOTHE WESTERN ELEC- TRIC COMPANY, OF CHICAGO, ILLINOIS.

METALLIC CIRCUIT FOR MULTIPLE SWITCH-BOARDS.

SPECIFICATION forming part of Letters Patent No. 357,539, dated February 8, 1887.

Application filed November 15, 1886.

To all whom it may concern:

Be it known that 1, JOHN A. SEELY, a'citiin the county of New York and State of New York, have invented a certain new and useful Improvement in Metallic Circuits for Multiple ing is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to metallic circuits for multiple switch boards of a telephone exchange; and its object is to provide for testing at any of the switch boards to determine whether any given line is in use. The springjack which I use may be of the form shown in Letters Patent No. 305,021, granted to C. E. Scribner October 9, 1884.

My invention consists in connecting one branch of the metallic circuit through a lever and its contact-point of a single switch on each of the switch-boards, andthence through an annunciator, and thence with the insulated frames or test-pieces of each of said switches, and thence to the subscribers switch-lever, and thence through the subscribers generator andbell included-in the circuit of the other branch, and in providing a branch connection to ground at the subscribers station,which is closed when the subscriber s telephone is hung upon his switchlever.

When the half connection or branchis closed from the metallic circuit to ground at the subscribers' station, it is evident that if the circuit, including a telephone and battery, be closed'to one of the test plates or rings of the line upon one of the switch-boards the battery will find circuit to the ground at the subscribers station,'and thus the operator by the click in his telephone will know that the subscribers telephone is hung up, and hence that the line is free. When the subscriber removes his telephone from his switch, the groundbranch is disconnected, and the branch containing his bell and generator is opened,while the telephone is looped into the circuit. In such case, there being no ground upon the metallic circuit, when atest is made at the central officenocircuit will be found to ground, and hence no current through the telephone, and the operator not hearing any click in his telephone will know that the line is not con- Serial No. 218.949. (No model.)

nected with ground at the subscribers station, and hence will know that the line is in use.

The key-board system which I use consists of looped plugs and pairs of double-stranded cords and switching apparatus, in connection with the calling-generator and operatorstelephone. This apparatus contains certain novel features which I have described and claimed in another application, and therefore will not describe the same in detail herein.

In the drawings, which are illustrative of my invention, Figure l is a diagram showing two metallic circuits connected, respectively, with their switches and individual annunciators on two multiple switch-boards, the multiple switch boards being shown in sections. Fig. 2 is a diagram illustrative of the circuits of a metallic circuit at a subscribers station. Fig. 3 is a detailed view of the loop-plug.

Like parts are indicated by similar letters of reference throughout the different figures.

I will trace the metallic circuit a as illustrated in Figs. 1 and 2. Beginning at the upper spring-jack upon the first board, the line a may be traced normally to the switch-lever of said switch, thence to the contact -point against which said lever normally rests, and in like manner through thespring-jack on the next board, thence through the subscribers individual shutter, and thence the line is branched to the metallic frames of each of said switches, and thence to the subscribers sta tion, where it is permanently connected with the subscriberstelephone switch-lever. From thence, when the telephone is hung upon the switch, the circuit may be traced through the generator and bell and back to the central office, thus completing the metallic circuit. When the telephone is hung upon the switch, as shown, at the subscribers station, the ground-branch b is closed to the telephoneswitch. Thus a ground-connection is formed at each subscribers station for each metallic circuit as long as the telephone of any given station remains upon the switch-lever. The subscriber on turning his generator will send current over the metallic circuit and throw down his shutter, thus notifying the operator at the central office of his call.

The different branches orsides of the metal lic circuit may be two of many wires included The branches or different in the same cable.

sides of the same metallic circuit preferably consist of insulated wires twisted together, so that they maybe in close proximity to one an other in the cable. Current sent over the metallic circuit thus formed has little or no injuri ous inductive effect upon other wires included in the same cable, as is well known. The operator on seeing the shutter fall inserts a loopplug in the switch of. the calling-subscriber, and looping in his telephone finds out what connection is wanted. He thereupon applies the tip of the plug to the test-ring of the subscriber wanted, to find out whether the line wanted is busy. If he hearsa cliekin his tele' phone as he taps thepoint of theplug against the test-ring, he infers that the line is free,-

and thereupon inserts the plug in the springjack and throws current to line of the subscriber wanted. Two subscribers are thus readily loopcdtogether in a metallic circuit, and when thus connected their calling-annunciatorswill not be included in the circuit, but will be in open branches, the branches being open at the switches of the lines in which the plugs are inserted.

Having thus described my invention, I claim as new and desire to secure by Letters Patent- 1. A metallic circuit connected through its switches on two or more multiple switchboards and through an annunciator, and

2. A telephone-line connected in a metallic,

circuit through a switch 011 each of the multiple switch-boards and thence through an annunciator and a branch connection to the insulated frames or test-pieces of said switches, in combinaticn with a loop-plug inserted in one of said switches, whereby the portion of the line including the individual annunciator is opened and the different branches or sides of the line connected with the different points of the loop-plug, substantially as shown and described.

In witness whereof I hereunto subscribe my name this 6th day of November, A. D. 1886.

JOHN A. SEELY.

Witnesses:

H. B. THAYER, A. L. SALT. 

